Shock and agitator tool

Abstract

A shock and agitator tool assembly vibrates a drill string to overcome stick slip and other friction-based problems that may occur during directional drilling. The agitator tool portion of the assembly, which can be used without the shock tool, allows for controlled activation and deactivation of the agitator tool by the use of one or more darts pumped downhole. The darts can be retrieved with a wireline tool. When activated, the agitator portion creates alternating pressure pulses. These pulses cause axial movement of the drill string above the agitator. A shock tool is described which utilizes a telescoping mandrel to amplify the axial movement created by the agitator tool.

We claim: 
     
       1. A downhole agitator tool for generating controlled vibrations of a drill string, comprising:
 a first dart, comprising:
 a dart body, open for fluid flow through the first dart; 
 a dart nose section having one or more openings for fluid flow through the first dart, coupled to the dart body; and 
 a dart nozzle disposed in the dart body, configured for a predetermined amount of fluid flow restriction, wherein the dart nozzle is separable from the dart body upon engagement of a second dart with the first dart; 
 
 a valve section, configured for vibration generation, comprising:
 an outer housing; 
 a driveshaft disposed radially interior to the outer housing, the driveshaft having a through bore and rotatable relative to the outer housing; 
 a driveshaft cap body disposed on an end of the driveshaft, in which are formed a first plurality of ports; and 
 a stationary rotary valve disposed radially exterior to the driveshaft cap body, in which are formed a second plurality of ports longitudinally aligned with the first plurality of ports; and 
 
 a power section, coupled to the valve section, comprising:
 a stator; 
 a rotor, disposed radially interior to the stator and coupled to the driveshaft; and 
 a dart catching unit, disposed on an uphole end of the rotor, comprising:
 a guide section forming a guide for receiving the first dart when pumped from uphole; and 
 a locking collet coupled to the guide section and configured to retain the first dart upon engagement, 
 
 
 wherein the power section rotor is stationary relative to the power section stator unless the first dart is engaged with the dart catching unit. 
 
     
     
       2. The downhole agitator tool of  claim 1 ,
 wherein the dart body comprises a groove configured for wireline retraction of the first dart uphole. 
 
     
     
       3. The downhole agitator tool of  claim 1 ,
 wherein the first plurality of ports comprises 2 ports, and 
 wherein the second plurality of ports comprises 4 ports. 
 
     
     
       4. The downhole agitator tool of  claim 1 ,
 wherein the second dart is configured to latch with the first dart upon engagement with the first dart. 
 
     
     
       5. The downhole agitator tool of  claim 1 , wherein the second dart is configured for a predetermined modified fluid flow rate when engaged with the first dart. 
     
     
       6. The downhole agitator tool of  claim 1 , wherein the first dart and the second dart are retrievable using a wireline tool. 
     
     
       7. The downhole agitator tool of  claim 1 , wherein the second dart is configured for engagement with a third dart pumped downhole. 
     
     
       8. A shock and agitator tool assembly, comprising:
 a shock tool, comprising:
 an outer housing; 
 an inner mandrel; and 
 one or more Belleville springs configured to allow axial movement of the inner mandrel relative to the outer housing, wherein the one or more Belleville springs are configured for compression corresponding to a predetermined downhole load; and 
 
 an agitator tool, comprising:
 a first dart, comprising:
 a dart body, open for fluid flow through the first dart; 
 a dart nose section having one or more openings for fluid flow through the first dart, coupled to the dart body; and 
 a dart nozzle disposed in the dart body, configured for a predetermined amount of fluid flow restriction, 
 wherein the dart nozzle is separable from the dart body upon engagement of a second dart with the first dart; 
 
 a valve section, configured for vibration generation, comprising:
 an outer housing; 
 a driveshaft disposed radially interior to the outer housing, the driveshaft having a through bore and rotatable relative to the outer housing; 
 a driveshaft cap body disposed on an end of the driveshaft, in which are formed a first plurality of ports; and 
 a stationary rotary valve disposed radially exterior to the driveshaft cap body, in which are formed a second plurality of ports longitudinally aligned with the first plurality of ports; and 
 
 a power section, coupled to the valve section, comprising:
 a stator; 
 a rotor, disposed radially interior to the stator and coupled to the driveshaft; and 
 a dart catching unit, disposed on an uphole end of the rotor, comprising:
 a guide section forming a guide for receiving the first dart when pumped from uphole; and 
 a locking collet coupled to the guide section and configured to retain the first dart upon engagement, 
 
 wherein the power section rotor is stationary relative to the power section stator unless the first dart is engaged with the dart catching unit. 
 
 
 
     
     
       9. The shock and agitator tool assembly of  claim 8 ,
 wherein the dart body comprises a groove configured for wireline retraction of the first dart uphole. 
 
     
     
       10. The shock and agitator tool assembly of  claim 8 ,
 wherein the first plurality of ports comprises 2 ports, and 
 wherein the second plurality of ports comprises 4 ports. 
 
     
     
       11. The shock and agitator tool assembly of  claim 8 ,
 wherein the second dart is configured to latch with the first dart upon engagement with the first dart. 
 
     
     
       12. The shock and agitator tool assembly of  claim 8 , wherein the second dart is configured for a predetermined modified fluid flow rate when engaged with the first dart. 
     
     
       13. The shock and agitator tool assembly of  claim 8 , wherein the first dart and the second dart are retrievable using a wireline tool. 
     
     
       14. The shock and agitator tool assembly of  claim 8 , wherein the second dart is configured for engagement with a third dart pumped downhole. 
     
     
       15. A method of controlling a downhole agitator tool, comprising:
 flowing drilling fluid through a bore of the agitator tool; 
 pumping a first dart downhole; 
 engaging the first dart with a dart catching region of the agitator tool; 
 reducing drilling fluid flow through the bore by a nozzle of the first dart; 
 engaging a power section of the agitator tool responsive to engaging the first dart with the dart catching region of the agitator tool; 
 rotating a rotary valve of the agitator tool by the power section, opening and restricting ports of the rotary valve, causing vibrations in the agitator tool at a predetermined frequency; 
 pumping a second dart downhole; and 
 engaging the second dart with the first dart, wherein the second dart further modifies drilling fluid flow through the bore. 
 
     
     
       16. The method of  claim 15 , further comprising:
 retrieving the first dart with a wireline tool; and 
 disengaging the power section responsive to retrieving the first dart. 
 
     
     
       17. The method of  claim 15 , wherein engaging the second dart with the first dart comprises:
 dislodging a nozzle carrier of the first dart by a nozzle plug of the second dart.